Abstract: A device for providing remote indication of the opening of a weighted pallet type tank vent in which a permanent magnet is attached to the end of the pallet guide shaft distal to the pallet. A magnetic induction sensor is secured to the outside of the shaft guide to sense movement of the magnetic field produced by the magnet and produce an electrical signal which may be transmitted to a remote location to indicate that the pallet has opened and relieved pressure in the tank.

Abstract: An apparatus and method for detecting lubricant reservoir levels, particularly in bearing sections for downhole mud motors, is revealed. This allows rig personnel to more exactly ascertain the remaining bearing life of the assembly. In one embodiment, the assembly is pulled out of the hole and comprises of a signal source. A hand-held device is placed next to the bearing housing and the location of the strongest signal is a direct measurement of the position of the floating piston in the lubricant reservoir. The rig personnel can then readily obtain a level reading on the fluid level in the reservoir. An alternative design is also revealed where the position of the floating piston is sensed in real-time by receivers mounted at spaced locations in the lubricant reservoir.

Abstract: A circuit board has an arcuate array of conductor segments each subject to a digital waveform differing in phase for the various segments, and a concentric pickup conductor. A rotary encoder disk has a conductive pattern which sums and couples the waveforms from selected segments, depending on rotary position, to the pickup conductor. A synchronous phase detector generates a phase signal from the summed waveforms and the zero crossing of the phase signal is detected. A counter develops count signals used to generate the digital waveforms. The count signals are input to a latch which is clocked at the zero crossing point to latch the count value which is a digital measure of the encoder angle.

Abstract: A liquid level detection apparatus has an outer semi-rigid, flexible tube closely surrounding an inner, non-permeable tube containing a magnetostrictive wire. The outer tube prevents collapse of the inner tube during bending and flexing of the inner tube to enable the inner tube to be bent or coiled during storage, shipping, and installation.

Abstract: A liquid level sensor for a tank includes coaxial inner and outer tubes having lower ends extending into the tank and upper ends projecting from the tank, with the upper end of the inner tube projecting from the outer tube and disposed a known distance from the top of the tank. A switch assembly includes a switch disposed in the inner tube and operable in response to proximity to a switch actuator which is carried by a float encircling the outer tube and movable therealong with the liquid level, the switch being connected across a pair of electrical conductors extending from the upper end of the inner tube. An indicator strip extends lengthwise of the conductors and is held thereagainst by a transparent sleeve, the strip having indicia indicating distance to the switch. Plastic cable ties extend through openings in the inner tube and snugly hold the switch assembly against the inner tube to permit manual axial movement of the switch assembly while preventing inadvertent movement thereof.

Abstract: A magnetostrictive position sensing device is disclosed where a probe assembly surrounding a waveguide is anchored at one end to the bottom of a tank and terminates in a transducer assembly attached to the top of the tank. The probe assembly compensates for differential coupling between two sections of the probe assembly. The sensing device also includes one or more fluid level floats movably surrounding a portion of the probe.

Abstract: A liquid gauging system for a liquid container, the system comprising sensor means for producing a first electromagnetic signal that corresponds to liquid quantity in the container, and remote interrogation means for receiving the first electromagnetic signal and producing a system output that corresponds to the liquid quantity; the sensor means being energized by a second electromagnetic signal transmitted by the remote interrogation means.

Abstract: 057238701Apparatus for detecting fluid level in a container, comprises a housing adapted to be disposed in the container; a float with an associated magnetic element, the float position corresponding to fluid level in the container; a magnetostrictive sensor disposed inside the housing; and a stick gauge disposed inside the housing; the magnetostrictive sensor and the stick gauge each being operable to determine the float position.

Abstract: An aboveground storage tank is provided with a mass balance system for quantitative detection of leakage of liquid from a tank. Arrays of temperature sensors measure the exterior wall temperature of the tank and temperature sensors in an open-ended standpipe within the tank measure the temperature of stored liquid. The temperature measurements and measurements of liquid level change in a chamber mounted at the upper end of the standpipe are polled at intervals to detect changes of the mass of liquid within the tank.

Abstract: Device for measuring a fill level of a container by means of a measuring sensor which is vertically adjustable contingent upon a surface level of liquid in the container, and which is connected to a travel-distance pickup, includes a source of compressed air directed towards the surface level and acting upon the measuring sensor so as to hold a lower end of the measuring sensor suspended at a defined distance above the surface level.

Abstract: A length measuring apparatus that uses an ultrasonic magnetostrictive delay line can detect a position with high accuracy by utilizing a reflected wave positively. In a measuring apparatus using an ultrasonic magnetostrictive delay line in which a wave transmitter (4) is disposed at one end of an ultrasonic magnetostrictive delay line (1), and the other end of the ultrasonic magnetostrictive delay line (1) is made an open end, a detecting coil (3) is wound around the outer periphery of the ultrasonic magnetostrictive delay line (1) over the whole area of the measuring range, a magnet piece (2) is disposed so as to become slidable along the ultrasonic magnetostrictive delay line (1) an a position of the magnet piece (2) is measured on the basis of a delay time of a detection pulse (B) produced in the detection coil (3) relative to a drive pulse (A) applied to the wave transmitter (4), a period (T.sub.

Abstract: A system for generating three-dimensional objects by creating a cross-sectional pattern of the object to be formed at a selected surface of a fluid medium capable of altering its physical state in response to appropriate synergistic stimulation by impinging radiation, particle bombardment or chemical reaction, successive adjacent laminae, representing corresponding successive adjacent cross-sections of the object, being automatically formed and integrated together to provide a step-wise laminar buildup of the desired object, whereby a three-dimensional object is formed and drawn from a substantially planar surface of the fluid medium during the forming process.

Abstract: Signal generating apparatus comprises a linear series of Hall-effect switches (44) arranged as a plurality of linear arrays in discrete probes (46a, 46b . . . 46n) which are butted end to end. Each switch is closed when in proximity of an actuating magnet (40) moveable along the series of switches. In each array a resistance chain (66) is linked at intervals to the switches. Movement of the magnet along an array thereby gives a progressively changing voltage on an output line (50) from the resistance chain as a cumulative signal indicating the position of the magnet. When the magnet moves from one array to the succeeding array after generating a maximum cumulative signal from said one array, that signal is maintained by a latch connection (56) between the two arrays. A cumulative signal representing the magnet position relative to the complete series of switches can thus be generated.

Abstract: An apparatus is provided for detecting the level of a liquid in a tank. The apparatus is designed to be connected to a controller that controls a pump so as to switch the pump on when the liquid level reaches a maximum authorized level and to stop operation of the pump when the level of the liquid has gone back down to a minimum level. The apparatus includes a float that is lifted by the liquid and that is guided vertically. The apparatus also includes a magnet that is carried by the float, and at least two switches each having contacts sealed in a capsule. Each switch is fixed in a horizontal fashion to a plate so as to correspond to a predetermined liquid level, and each switch turns on an electrical circuit connected to the controller when the switch is in the magnetic field of the magnet. The plate is disposed in a vertical plane that is parallel to and in close proximity to the displacement of the float.

Abstract: A damping element for use with a waveguide that supports a current pulse and results in a torsional or longitudinal strain wave is disclosed. The damping element is to dampen the reflection of the strain wave and includes a sleeve surrounding the waveguide and a mechanism for applying pressure on the sleeve so the sleeve exerts pressure on the waveguide, thereby gradually dampening the strain wave energy along the length of the waveguide surrounded by the damping element sleeve to prevent reflection of the strain wave.

Abstract: An oil spill detection system to detect and track oil spills and transmit data to a remote monitoring center comprising a buoyant detection platform including at least one detection sensor to detect the presence of hydrocarbons in the water adjacent the buoyant detection platform and generate a detection signal in response thereto and a communication system operatively coupled to the detection sensor to receive the detection signal and to generate a data signal in response to the detection signal and to transmit the data signal to the remote monitoring center, the data signal including a discrete platform identification signal corresponding to the buoyant detection platform, and a deployable free floating tracking buoy to be deployed when the detection signal is generated to indicate the direction and speed of travel of the oil slick created by the oil spill.

Abstract: A fuel recovery system warns a user of an impending overflow of fuel and also provides an overflow chamber into which relatively small amount of overfilled fuel are captured, thus preventing fuel spillage into the surrounding environment. The system is adapted for use with a fuel tank attached to a fuel fill line and an overflow line, and comprises a float assembly adapted to be coupled inline to the overflow line; an overflow chamber coupled via a check valve to the main fuel tank; and an optical/electronic warning system for warning the user when fuel in the float assembly rises to a predetermined level.

Abstract: An improved magnetostrictive wire based position transducer that has applications in both liquid level measuring systems and in position indicating systems. A cylindrically structured and circularly polarized piezoelectric element directly measures the torsional acoustic waves in the magnetostrictive wire as they are received by the sensor. The cylindrical structure of the sensor eliminates many of the inadvertently detected acoustic and electrical pulses within the wire that are not indicative of the passage of the torsional wave of concern. The present system provides an improved sensor configuration which is selectively sensitive to torsional waves while being insensitive to vibrations in alternate planes. This improved piezoelectric sensor in combination with the electrical configuration allows placement of the magnetostrictive wire apart from the liquid whose level is being measured or from the indicator whose position is of concern.

Abstract: A leak detector including a float having a number of magnets connected to the float. Electromagnetic coils are disposed along a length of the possible range of travel of the float within the leak detector. The coils, when energized, interact with the magnet making the float move-about and settle to a position representing its true equilibrium buoyancy. Optionally, the leak detector includes a self-calibration apparatus that provides a reference signal indicting the fixed position of the self-calibration apparatus, allowing the leak detector to compensate for offset errors.

Abstract: The present application discloses a magnetostrictive linear displacement detector with an axial coil torsional strain transducer. The displacement detector includes a magnetostrictive wire, a return wire and a magnet disposed for displacement along the magnetostrictive wire. A torsional strain sensor at the head end generates an electrical indication of the torsional strain within the magnetostrictive wire induced by passage of an electrical excitation by the position of the magnet. The torsional strain sensor includes two serially connected coils wound in opposite directions. The total length is short compared with the rate of electrical propagation within the magnetostrictive wire and long compared with the rate of torsional strain propagation within the magnetostrictive wire. The induced current within the two coils from electrical excitation of the magnetostrictive wire substantially cancel out because generally the whole sensor is excited simultaneously.

Abstract: A variable rejection level system for a magnetostrictive transducer which improves the detectability of magnetostrictive pulses along a waveguide in the presence of background noise on the waveguide.

Abstract: A stereolithographic system for automatically generating three-dimensional objects on a layer by layer basis by alternately forming layers of medium over previously formed layers of the object and selectively solidifying successive layers of medium at a surface of a body of the medium whereby the object is formed from a plurality of solidified and adhered layers. The surface of the body of medium is maintained at a desired working surface, for example by detecting its level and relatively adjusting it and the working surface so that they coincide.

Abstract: A magnetic sight gage sensor comprises a sensor for determining the liquid level in a process vessel utilizing a magnetic float on the interior of a tube. The tube is connected at different levels to a process vessel and contains a liquid that is maintained at the same level as the liquid inside the process vessel. A magnetostrictive displacement transducer is coupled to the tube or sight glass on the exterior of such glass, so it is out of the process fluid. The transducer provides signals indicating the position of the float relative to a reference position on the transducer. The tube or sight glass is made of a non-magnetic material in order to allow transmission of the magnetic field from the float to the transducer.

Abstract: A linear sensing device containing an electrically conductive reed strip which, in the presence of an external actuating horseshoe magnet, makes electrical contact to a resistive strip at the location of that magnet. The conductive reed strip is attached along one end to a supporting member, formed from a material with coefficient of thermal expansion similar to the reed strip, to prevent warping of the reed strip over a range of environmental temperatures. The sensing device is of a modular construction with elongate cap, to which the resistive strip is attached, and an elongate base, to which the reed strip support member is attached. The cap and base mate together to form an inner container which then slides into an outer container.

Abstract: A fluid level maintenance sensor or use in a tank test system and which includes an upper sensor coil and a lower sensor coil mounted on a level sensing tube. A float carrying a ferromagnetic ring is operatively mounted in the level sensing tube which causes a fluid transfer signal to be generated when the float and ring are moved upwardly or downwardly to transfer fluid out or into the level sensing tube to maintain a selected fluid level in the tube.

Abstract: A reservoir, provided with a device for warning when the level of an operation fluid to be supplied to a fluid pressure master cylinder drops below a given level, comprises a fluid tank for storage of the operation fluid and a float chamber with an upper wall provided on the side portion of the fluid tank. A reed switch for the fluid level drop warning device is provided at the lower portion of the float chamber, and a float having a magnet is retained in the float chamber. A partition for restricting the movement of the float is detachably mounted at the communicating section between the fluid tank and float chamber. This arrangement facilitates the mounting and replacement of the float and reed switch.

Abstract: A magnetostrictive linear displacement detector with increased position resolution includes a magnetostrictive wire anchored at opposite head and foot ends with a reflection termination at the foot end and a damping termination at the head end. A return wire is connected to the foot end of the magnetostrictive wire. The magnetostrictive wire is electrically excited at its head end. A variable position to be detected is represented by a magnet disposed for displacement along the magnetostrictive wire. A torsional motion sensor at the head end generates an electrical indication of the torsional motion within the magnetostrictive wire induced by passage of the electrical excitation by the position of the magnet. The displacement is determined from the interval of time between the detection of the torsional motion traveling directly from the magnet and the detection of the torsional motion reflected from the reflection termination.

Abstract: There is provided between a concentrate tank and a membrane filter a circulating line which consists of a feed line and a return line. It is also possible to use an ultrafilter as the membrane filter. There is provided a leveling tube connected by respective pipes to the concentrate tank at top and bottom portions thereof, respectively. A buoy floats within the leveling tube and a position of this buoy is detected by means of transparency of the leveling tube itself or photosensors in order to detect a degree of concentration of the culture fluid progressing within the concentrate tank. There may be provided multi-stage circulating lines each connecting the associated concentrate tank to the associated membrane filter so that the culture fluid can be transferred during the process of concentration from the stage of the largest volume treatment to the state of the least volume treatment in order to concentrate the culture fluid more efficiently.

Abstract: In a device for monitoring the liquid level in a tank, utilizing a reed switch projecting into the tank in an internally cylindrical hollow rod and a float provided with a permanent magnet and guided on the hollow rod, the reed switch is constructed as an independent exchangeable part introducible into the hollow rod with an accurate fit and with a small assembly outlay. The slide-in part has three radially resilient abutment zones distributed uniformly around the circumference. In order to accurately introduce the slide-in part into the hollow rod, with a minimum of force, three axial guide grooves associated with the resilient abutment zones are formed radially outwards in the inner envelope surface of the hollow rod. In order to achieve the final accurate fit, the slide-in part, introduced completely into the hollow rod, is rotated until the resilient abutment zones are located in regions between the guide grooves of the hollow rod.

Abstract: The position sensor of the present invention includes a pair of elongated conducting members disposed in a parallel arrangement and a conducting metallic ball or mercury drop freely movable following the pair of elongated conducting members while maintaining a simultaneous contact with the pair of elongated conducting members, which combination provides two electric circuits respectively including a first circuit including a first poriton of the two elongated conducting members and the contact provided by the metallic ball or mercury drop, and a second electric circuit including the second portion of the two elongated conducting members and the same contact, wherein the metallic ball or mercury drop divides the combination of the two elongated conducting members into the first and second portions.

Abstract: A displacement transducer utilizes a torsional strain waveguide having a magnetic member that is adjustable positioned along the length of the waveguide, when an electrical current pulse is passed along the waveguide and reaches the magnet torsional strain wave is created in the waveguide. The torsional strain wave will be reflected back toward a mounting end of the waveguide where a converter or sensor is positioned to sense the strain wave signal and convert it to an electrical output signal. The strain wave signals have signal lobes of a time period. A waveguide mounting block supports the waveguide at the mounting end and provides a reflection point for the torsional strain waves. The waveguide mounting block is on an opposite side of the signal sensor from the magnet.

Abstract: A position sensor and method for detecting and providing an indication of the position of a movable member comprising a ferromagnetic element oriented substantially parallel to the path of travel of the movable member, the element including a segment thereof having spaced-apart ends defining the positional limits between which movement of the movable member is to be monitored, the segment comprising a pair of contiguous, oppositely polarized, remanently magnetized regions defining an intersection along the length of the segment; a magnet positioned proximate the intersection and mounted in known spatial relationship to the movable member for movement therewith, and, simultaneously along the ferromagnetic element, the magnet providing a magnetic field presenting a constant polarity to the element and having a strength sufficient to locally polarize the element, whereby movement of the magnet means along the element alters the length of the respective regions; and, means for sensing the position of the intersec

Abstract: A liquid level detector of the type in which a magnetostrictive wire extends through the liquid level measurement range and is captured in a tensioned vertical orientation within a stainless steel tube. Liquid level is measured as a function of the time required for a torsional disturbance imparted the wire near the top to travel along the wire to a magnet which is contained within a liquid level float which slides up and down along the tube. The torsional disturbances imparted to the wire by means of a piezoelectric crystal to which the wire is easily clamped. Accuracy is enhanced by measuring liquid level as a function of the elapsed time between an actuation signal and the first zero crossing of the voltage which is induced as the torsional strain passes through the area of influence of the sliding magnet.

Abstract: A sonic delay line assembly suitable for shipping in coiled form allowing for expedited installation, particularly in liquid storage tanks. The sonic delay line comprises a sonic waveguide made of solid wire, which also serves as an electrical pulse conductor for the generation of sonic pulses on waveguide through interaction with a positionable static magnetic field. A sonic waveguide containment can be provided to protect the flexible tubing and sonic waveguide. Positioned around the containment and free to ride up and down the containment as liquid levels in the tank vary is a float. The float carries an annular magnet with poles axially aligned with sonic waveguide to provide the magnetic field with which the magnetic fields of the electrical pulses on the sonic waveguide interact.

Abstract: A groundwater pollutant recovery system using the cone of depression approach, in which a sensing probe having liquid level sensors responsive to both water and pollutant levels and having attached to it the pollutant intake is deployed in a recovery well above the submerged water and pollutant pumps. The pollutant intake on the sensing probe is attached to the pollutant pump by an extendable hose so that the sensing probe may be raised and lowered in response to changing hydraulic conditions in the well without the necessity of changing the water or pollutant pump positions. The recovery sequence is controlled by a microprocessor under the control of a program responsive to the liquid levels indicated by the sensors in the sensing probe.

Abstract: An apparatus is disclosed for determining the thickness of a layer of aerated sludge floating on a layer of heavier liquid in a tank used in the treatment of sewage. The apparatus comprises a frame which can be positioned to extend vertically into the tank, an indicator supported by and movable vertically with respect to the frame, the indicator being positionable at the highest level of sludge in the tank, a horizontally-extending lower base attached to the frame at or near the bottom thereof, a horizontally-extending upper base attached to the frame at or near the top thereof, and a line carrying a float, the line being movably secured at the upper and lower base. The float is movable between the upper and lower base, is floatable on the liquid, and includes a horizontally extending portion presenting an upwardly directed, generally planar surface.

Abstract: The liquid level in a tank is determined by measuring the current supplied to an elctromagnet from which a rod having a specific gravity greater than that of the liquid is suspended in the liquid.

Abstract: Apparatus for detecting the level of a liquid. A metal-detecting proximity sensor is placed near a non-metallic, vertically-positioned guide shaft. A float is placed on the liquid. A tube has one end attached to the float and the other end insertably placed within the guide shaft. A piece of metal is placed within the tube. When the apparatus is used for determining when the level of the liquid reaches a predetermined value, the metal piece has a boundary which is located at the height of the proximity sensor only when the liquid level is at its predetermined value. When the apparatus is used for measuring the level of the liquid, the proximity sensor has an output signal proportional to the distance from itself to metal and the metal piece has an outer surface whose distance to the proximity sensor at the height of the proximity sensor, changes with changes in the liquid level.

Abstract: A liquid level detector of the type in which a magnetostrictive wire extends through the liquid level measurement range and is captured in a tensioned vertical orientation within a stainless steel tube. Liquid level is measured as a function of the time required for a torsional disturbance imparted the wire near the top to travel along the wire to a magnet which is contained within a liquid level float which slides up and down along the tube. The torsional disturbances imparted to the wire by means of a piezoelectric crystal to which the wire is easily clamped. Accuracy is enhanced by measuring liquid level as a function of the elapsed time between an actuation signal and the first zero crossing of the voltage which is induced as the torsional strain passes through the area of influence of the sliding magnet.

Abstract: A mode converter for a distance measuring device having a sonic delay line with a permanent magnet movable along same, the converter having a free-standing magnetostrictive armature with one end attached to the delay line and the other end terminating dampinglessly within the usual coil. The armature length and shape are such that the longitudinal stress wave initiated by an electrical pulse in the coil strengthens the mechanical pulse applied to the delay line.

Abstract: A measuring device includes means for converting a physical quantity to be measured into a corresponding magnetic field. A magnetooptic element is aligned with a polarizer which passes incident light in one plane only. The part of the magnetooptic element which intercepts the transmitted magnetic field rotates the throughgoing light and the position of rotation is indicated on an optical indicator.

Abstract: An apparatus for detecting and maintaining the level of a liquid in a container filling machine having a rotatable filler bowl includes a float disposed within the liquid in the bowl and having a permanent magnet disposed within the float body. A liquid level indicating bar is mounted within the bowl and is formed from a magnetically responsive material so that vertical movement of the float results in a vertical movement of the liquid level indicating bar. An infrared photo detector is provided for detecting the position of the liquid level indicator and controls are provided for increasing or decreasing the rate of flow of liquid into the bowl depending on the detected level of the liquid.

Abstract: This invention pertains to gauge apparatus for measuring liquid levels comprising an elongated electrical sensor adapted to be arranged in upright position while immersed so constructed as to have an electrical resistance which may be varied. A spherical float is magnetically attracted to the sensor for rolling movement with respect thereto for varying the resistance in response to variation in elevation of float caused by changes in the level of the liquid. The resistance is measured thereby to provide an indication of such level. The magnetic attraction holds the float and sensor in operative engagement at all times including those during which the float changes height in response to changes in the level of the liquid being measured. The presence of different liquid is also detected in a given vessel, such as gasoline and water, and an indication and alarm of vessel overfill during a filling operation is provided.

Abstract: A fluid measurement gauge is principally used to measure the fluid level in large underground storage tanks, such as for storing gasoline at service stations. A housing is positioned vertically in the fluid and includes a leadscrew which is driven by a stepper motor. A nut is mounted for longitudinal movement along the leadscrew. A float encircles the housing and includes a magnet at the surface of the fluid level. A magnetic sensor, such as a Hall-effect switch, is mounted on the nut and driven in selected steps downward to encounter the magnet mounted in the float. A reference position is marked at the top of the housing and the fluid level is measured downward from the reference position by detecting the magnet by operation of the magnetic sensor. An additional float can be provided to detect the interface between two fluids such as gasoline and water. The second float is further provided with a magnet to be detected by the magnetic sensor.

Abstract: A liquid level indicator includes a magnetized float and a plurality of magnetized indicator elements which are pivoted by the float magnet and which have distinguishable opposite surfaces to provide the liquid level indication, the indicator elements being formed from a material which provides magnetic fields of opposite magnetic polarity which extend substantially continuously along the opposite edges of the indicator elements.

Abstract: The specification discloses a method and apparatus for detecting the position of the float in a glass tube flow meter, and determining the distance of said float from a reference line on the glass tube flow meter which is being calibrated. The blockage of an infrared light beam being sent from a transmitter to dual photo receivers, coupled to an optical conditioner circuit, provides an indication of whether float is high, low or in-band in relationship to the desired position, while a float follower, which is movable along the length of the flow tube by a stepper motor which is connected to a pulse encoder, provides through an optical conditioner circuit, an indication of the float position with regard to the reference line on the glass tube. The circuitry also provides for the automatic tracking of the float as its position is changed by the operator.

Abstract: A flexible stick tank gauge is made of a thin metal or plastic tape. The tape is sufficiently thick to be self-supporting when held vertically from the lower end. Alternatively, the tape is curved to be a narrow sector of a cylinder. Measuring indicia are applied to at least one surface of the tape. The tape remains flexible at extreme environments of temperatures and will not break in normal use such as airline fuel measuring operations.

Abstract: A direct reading tank gauge is made of plastic tape or thin metal in an endless loop. Measuring indicia are applied to one surface of the tape in a display tape assembly. An armature is fixedly mounted to the tape. A tank float is magnetically coupled to the armature, which follows the float and fluid level. A hinged window enables visual observation of tape indicia representing the position of the float, armature and liquid level and removal of the entire display tape assembly for service or repair.

Abstract: An improved indicator for fill content of a fire extinguishing system including a pressure vessel having an outlet through which the fire extinguishing material may flow. The indicator includes a non-magnetic, closed housing, mounted on the vessel and having one end within the vessel and the other end exteriorly of the vessel. At least one of the vessel and the housing are sealed to the atmosphere and a visual access opening is provided on the exterior end of the housing to allow one to look into the interior of the housing. A tape is mounted within the housing for movement in a path past the visual access opening and includes indicia along its length.

Abstract: An apparatus and method for checking and measuring the momentary value of a variable physical magnitude, such as a volume of liquid in a container or tank, or a temperature, viscosity, or velocity, for example. The invention comprises a transducer free to follow without friction the variations of the physical magnitude, such as for example the level of a liquid fluid in a reservoir, the transducer having a portion of progressively varying cross-section displaceable as a function of the changes in the physical magnitude disposed in alignment with a sensor normally positioned in a reference position out of contact from the transducer.